[PATCH 0/1] MIPS: fix compilation error

[PATCH 0/1] MIPS: fix compilation error

[Mauri Sandberg]

Hello!

I hit into a compilation error while making a build for ath79
It apparently seems to have a trivial fix but I cannot say for sure with
superficial investigation. Adding into CC: the author and reviewer of the
commit that appears to be the root cause. You might have a better
understanding of the causes and consequences.

Root cause:
commit b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")

When reproducing the error my diff of the default ath79_defconfig is:
-# CONFIG_RD_GZIP is not set
+CONFIG_INITRAMFS_SOURCE="initramfs.txt"
-CONFIG_MIPS_CMDLINE_FROM_DTB=y
+CONFIG_PRINTK_TIME=y
-CONFIG_CMDLINE="rootfstype=squashfs,jffs2"
+CONFIG_CMDLINE="console=ttyS0,115200 rootfstype=ramfs"
+CONFIG_CMDLINE_OVERRIDE=y

Cheers,
Mauri

Mauri Sandberg (1):
  MIPS: kernel: setup.c: fix compilation error

 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


base-commit: 509d36a941a3466b78d4377913623d210b162458
-- 
2.25.1

[PATCH 1/1] MIPS: kernel: setup.c: fix compilation error

[Mauri Sandberg]

Developing against mips/mips-next I get a compilation error.
With the attached patch compilation succeeds.

Build log:
...
  CC      kernel/locking/percpu-rwsem.o
../arch/mips/kernel/setup.c:46:39: error: conflicting types for
'__appended_dtb'
 const char __section(".appended_dtb") __appended_dtb[0x100000];
                                       ^~~~~~~~~~~~~~
In file included from ../arch/mips/kernel/setup.c:34:
../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
of '__appended_dtb' was here
 extern char __appended_dtb[];
             ^~~~~~~~~~~~~~
  CC      fs/attr.o
make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
 Error 1
make[3]: *** [../scripts/Makefile.build:514: arch/mips/kernel] Error 2
make[2]: *** [/home/ubuntu/git/linux/Makefile:1849: arch/mips] Error 2
make[2]: *** Waiting for unfinished jobs....
...

Root cause seems to be:
commit b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")

Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
---
 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 279be0153f8b..23a140327a0b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -43,7 +43,7 @@
 #include <asm/prom.h>
 
 #ifdef CONFIG_MIPS_ELF_APPENDED_DTB
-const char __section(".appended_dtb") __appended_dtb[0x100000];
+char __section(".appended_dtb") __appended_dtb[0x100000];
 #endif /* CONFIG_MIPS_ELF_APPENDED_DTB */
 
 struct cpuinfo_mips cpu_data[NR_CPUS] __read_mostly;
-- 
2.25.1

[PATCH v2 0/1] MIPS: fix compilation error

[Mauri Sandberg]

Earlier I had some confusion with my configuration as compared to
ath79_defconfig but now it looks like that enabling
CONFIG_MIPS_ELF_APPENDED_DTB alone will break compilation.

Simple fix of removing 'const' did not work and something more is needed.
At this point I would suggest reverting the patch until it's properly
fixed.

I am willing to help with testing if that is needed.

Thanks,
Mauri

Mauri Sandberg (1):
  Revert "MIPS: of: Introduce helper function to get DTB"

 arch/mips/ath79/setup.c               | 13 ++++++-----
 arch/mips/bmips/setup.c               |  7 +++---
 arch/mips/generic/init.c              |  5 +++--
 arch/mips/include/asm/bootinfo.h      | 22 +------------------
 arch/mips/include/asm/octeon/octeon.h |  1 +
 arch/mips/kernel/head.S               | 31 +++++++++++++++++++++++++++
 arch/mips/kernel/setup.c              |  4 ++++
 arch/mips/lantiq/prom.c               |  7 ++++--
 arch/mips/pic32/pic32mzda/init.c      | 15 ++++++++++++-
 arch/mips/ralink/of.c                 | 11 +++++++---
 10 files changed, 77 insertions(+), 39 deletions(-)


base-commit: 509d36a941a3466b78d4377913623d210b162458
-- 
2.25.1

[PATCH v2 1/1] Revert "MIPS: of: Introduce helper function to get DTB"

[Mauri Sandberg]

Ath79 does not compile if CONFIG_MIPS_ELF_APPENDED_DTB is enabled. Simple
removal of 'const' fixes compilation but booting a device is stopped
short.

This reverts commit b83ba0b9df56f8404ccc6ebcc7050fb8294f0f20.

Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
---
 arch/mips/ath79/setup.c               | 13 ++++++-----
 arch/mips/bmips/setup.c               |  7 +++---
 arch/mips/generic/init.c              |  5 +++--
 arch/mips/include/asm/bootinfo.h      | 22 +------------------
 arch/mips/include/asm/octeon/octeon.h |  1 +
 arch/mips/kernel/head.S               | 31 +++++++++++++++++++++++++++
 arch/mips/kernel/setup.c              |  4 ++++
 arch/mips/lantiq/prom.c               |  7 ++++--
 arch/mips/pic32/pic32mzda/init.c      | 15 ++++++++++++-
 arch/mips/ralink/of.c                 | 11 +++++++---
 10 files changed, 77 insertions(+), 39 deletions(-)

diff --git a/arch/mips/ath79/setup.c b/arch/mips/ath79/setup.c
index 891f495c4c3c..7e7bf9c2ad26 100644
--- a/arch/mips/ath79/setup.c
+++ b/arch/mips/ath79/setup.c
@@ -213,17 +213,16 @@ unsigned int get_c0_compare_int(void)
 
 void __init plat_mem_setup(void)
 {
-	void *dtb;
+	unsigned long fdt_start;
 
 	set_io_port_base(KSEG1);
 
 	/* Get the position of the FDT passed by the bootloader */
-	dtb = (void *)fw_getenvl("fdt_start");
-	if (dtb == NULL)
-		dtb = get_fdt();
-
-	if (dtb)
-		__dt_setup_arch((void *)KSEG0ADDR(dtb));
+	fdt_start = fw_getenvl("fdt_start");
+	if (fdt_start)
+		__dt_setup_arch((void *)KSEG0ADDR(fdt_start));
+	else if (fw_passed_dtb)
+		__dt_setup_arch((void *)KSEG0ADDR(fw_passed_dtb));
 
 	ath79_reset_base = ioremap(AR71XX_RESET_BASE,
 					   AR71XX_RESET_SIZE);
diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index 31bcfa4e08b9..7392edbd19e7 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -161,10 +161,11 @@ void __init plat_mem_setup(void)
 	/* intended to somewhat resemble ARM; see Documentation/arm/booting.rst */
 	if (fw_arg0 == 0 && fw_arg1 == 0xffffffff)
 		dtb = phys_to_virt(fw_arg2);
+	else if (fw_passed_dtb) /* UHI interface or appended dtb */
+		dtb = (void *)fw_passed_dtb;
+	else if (&__dtb_start != &__dtb_end)
+		dtb = (void *)__dtb_start;
 	else
-		dtb = get_fdt();
-
-	if (!dtb)
 		panic("no dtb found");
 
 	__dt_setup_arch(dtb);
diff --git a/arch/mips/generic/init.c b/arch/mips/generic/init.c
index 1842cddd8356..68763fcde1d0 100644
--- a/arch/mips/generic/init.c
+++ b/arch/mips/generic/init.c
@@ -39,13 +39,14 @@ void __init *plat_get_fdt(void)
 		/* Already set up */
 		return (void *)fdt;
 
-	fdt = (void *)get_fdt();
-	if (fdt && !fdt_check_header(fdt)) {
+	if (fw_passed_dtb && !fdt_check_header((void *)fw_passed_dtb)) {
 		/*
 		 * We have been provided with the appropriate device tree for
 		 * the board. Make use of it & search for any machine struct
 		 * based upon the root compatible string.
 		 */
+		fdt = (void *)fw_passed_dtb;
+
 		for_each_mips_machine(check_mach) {
 			match = mips_machine_is_compatible(check_mach, fdt);
 			if (match) {
diff --git a/arch/mips/include/asm/bootinfo.h b/arch/mips/include/asm/bootinfo.h
index 5be10ece3ef0..aa03b1237155 100644
--- a/arch/mips/include/asm/bootinfo.h
+++ b/arch/mips/include/asm/bootinfo.h
@@ -112,27 +112,7 @@ extern char arcs_cmdline[COMMAND_LINE_SIZE];
 extern unsigned long fw_arg0, fw_arg1, fw_arg2, fw_arg3;
 
 #ifdef CONFIG_USE_OF
-#include <linux/libfdt.h>
-#include <linux/of_fdt.h>
-
-extern char __appended_dtb[];
-
-static inline void *get_fdt(void)
-{
-	if (IS_ENABLED(CONFIG_MIPS_RAW_APPENDED_DTB) ||
-	    IS_ENABLED(CONFIG_MIPS_ELF_APPENDED_DTB))
-		if (fdt_magic(&__appended_dtb) == FDT_MAGIC)
-			return &__appended_dtb;
-
-	if (fw_arg0 == -2) /* UHI interface */
-		return (void *)fw_arg1;
-
-	if (IS_ENABLED(CONFIG_BUILTIN_DTB))
-		if (&__dtb_start != &__dtb_end)
-			return &__dtb_start;
-
-	return NULL;
-}
+extern unsigned long fw_passed_dtb;
 #endif
 
 /*
diff --git a/arch/mips/include/asm/octeon/octeon.h b/arch/mips/include/asm/octeon/octeon.h
index 7e714aefc76d..08d48f37c046 100644
--- a/arch/mips/include/asm/octeon/octeon.h
+++ b/arch/mips/include/asm/octeon/octeon.h
@@ -282,6 +282,7 @@ union octeon_cvmemctl {
 extern void octeon_check_cpu_bist(void);
 
 int octeon_prune_device_tree(void);
+extern const char __appended_dtb;
 extern const char __dtb_octeon_3xxx_begin;
 extern const char __dtb_octeon_68xx_begin;
 
diff --git a/arch/mips/kernel/head.S b/arch/mips/kernel/head.S
index b825ed4476c7..61b73580b877 100644
--- a/arch/mips/kernel/head.S
+++ b/arch/mips/kernel/head.S
@@ -93,6 +93,33 @@ NESTED(kernel_entry, 16, sp)			# kernel entry point
 	jr	t0
 0:
 
+#ifdef CONFIG_USE_OF
+#if defined(CONFIG_MIPS_RAW_APPENDED_DTB) || \
+	defined(CONFIG_MIPS_ELF_APPENDED_DTB)
+
+	PTR_LA		t2, __appended_dtb
+
+#ifdef CONFIG_CPU_BIG_ENDIAN
+	li		t1, 0xd00dfeed
+#else  /* !CONFIG_CPU_BIG_ENDIAN */
+	li		t1, 0xedfe0dd0
+#endif /* !CONFIG_CPU_BIG_ENDIAN */
+	lw		t0, (t2)
+	beq		t0, t1, dtb_found
+#endif /* CONFIG_MIPS_RAW_APPENDED_DTB || CONFIG_MIPS_ELF_APPENDED_DTB */
+	li		t1, -2
+	move		t2, a1
+	beq		a0, t1, dtb_found
+
+#ifdef CONFIG_BUILTIN_DTB
+	PTR_LA	t2, __dtb_start
+	PTR_LA	t1, __dtb_end
+	bne		t1, t2, dtb_found
+#endif /* CONFIG_BUILTIN_DTB */
+
+	li		t2, 0
+dtb_found:
+#endif /* CONFIG_USE_OF */
 	PTR_LA		t0, __bss_start		# clear .bss
 	LONG_S		zero, (t0)
 	PTR_LA		t1, __bss_stop - LONGSIZE
@@ -106,6 +133,10 @@ NESTED(kernel_entry, 16, sp)			# kernel entry point
 	LONG_S		a2, fw_arg2
 	LONG_S		a3, fw_arg3
 
+#ifdef CONFIG_USE_OF
+	LONG_S		t2, fw_passed_dtb
+#endif
+
 	MTC0		zero, CP0_CONTEXT	# clear context register
 #ifdef CONFIG_64BIT
 	MTC0		zero, CP0_XCONTEXT
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 279be0153f8b..2546f2fd2eb6 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -784,6 +784,10 @@ void __init setup_arch(char **cmdline_p)
 unsigned long kernelsp[NR_CPUS];
 unsigned long fw_arg0, fw_arg1, fw_arg2, fw_arg3;
 
+#ifdef CONFIG_USE_OF
+unsigned long fw_passed_dtb;
+#endif
+
 #ifdef CONFIG_DEBUG_FS
 struct dentry *mips_debugfs_dir;
 static int __init debugfs_mips(void)
diff --git a/arch/mips/lantiq/prom.c b/arch/mips/lantiq/prom.c
index bc9f58fcbdf9..363937121617 100644
--- a/arch/mips/lantiq/prom.c
+++ b/arch/mips/lantiq/prom.c
@@ -73,8 +73,11 @@ void __init plat_mem_setup(void)
 
 	set_io_port_base((unsigned long) KSEG1);
 
-	dtb = get_fdt();
-	if (dtb == NULL)
+	if (fw_passed_dtb) /* UHI interface */
+		dtb = (void *)fw_passed_dtb;
+	else if (&__dtb_start != &__dtb_end)
+		dtb = (void *)__dtb_start;
+	else
 		panic("no dtb found");
 
 	/*
diff --git a/arch/mips/pic32/pic32mzda/init.c b/arch/mips/pic32/pic32mzda/init.c
index 764f2d022fae..1897aa863573 100644
--- a/arch/mips/pic32/pic32mzda/init.c
+++ b/arch/mips/pic32/pic32mzda/init.c
@@ -21,11 +21,24 @@ const char *get_system_type(void)
 	return "PIC32MZDA";
 }
 
+static ulong get_fdtaddr(void)
+{
+	ulong ftaddr = 0;
+
+	if (fw_passed_dtb && !fw_arg2 && !fw_arg3)
+		return (ulong)fw_passed_dtb;
+
+	if (&__dtb_start < &__dtb_end)
+		ftaddr = (ulong)__dtb_start;
+
+	return ftaddr;
+}
+
 void __init plat_mem_setup(void)
 {
 	void *dtb;
 
-	dtb = get_fdt();
+	dtb = (void *)get_fdtaddr();
 	if (!dtb) {
 		pr_err("pic32: no DTB found.\n");
 		return;
diff --git a/arch/mips/ralink/of.c b/arch/mips/ralink/of.c
index 8286c3521476..2c9af61efc20 100644
--- a/arch/mips/ralink/of.c
+++ b/arch/mips/ralink/of.c
@@ -64,15 +64,20 @@ static int __init early_init_dt_find_memory(unsigned long node,
 
 void __init plat_mem_setup(void)
 {
-	void *dtb;
+	void *dtb = NULL;
 
 	set_io_port_base(KSEG1);
 
 	/*
 	 * Load the builtin devicetree. This causes the chosen node to be
-	 * parsed resulting in our memory appearing.
+	 * parsed resulting in our memory appearing. fw_passed_dtb is used
+	 * by CONFIG_MIPS_APPENDED_RAW_DTB as well.
 	 */
-	dtb = get_fdt();
+	if (fw_passed_dtb)
+		dtb = (void *)fw_passed_dtb;
+	else if (&__dtb_start != &__dtb_end)
+		dtb = (void *)__dtb_start;
+
 	__dt_setup_arch(dtb);
 
 	of_scan_flat_dt(early_init_dt_find_memory, NULL);
-- 
2.25.1

Re: [PATCH v2 0/1] MIPS: fix compilation error

[Thomas Bogendoerfer]

On Fri, Mar 26, 2021 at 06:46:44PM +0200, Mauri Sandberg wrote:
> Earlier I had some confusion with my configuration as compared to
> ath79_defconfig but now it looks like that enabling
> CONFIG_MIPS_ELF_APPENDED_DTB alone will break compilation.
> 
> Simple fix of removing 'const' did not work and something more is needed.

your first fix works perfect for me. Could please describe what the error
is ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH v2 0/1] MIPS: fix compilation error

[Mauri Sandberg]

> ----------------------------------------
> From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> On Fri, Mar 26, 2021 at 06:46:44PM +0200, Mauri Sandberg wrote:
> > Earlier I had some confusion with my configuration as compared to
> > ath79_defconfig but now it looks like that enabling
> > CONFIG_MIPS_ELF_APPENDED_DTB alone will break compilation.
> > 
> > Simple fix of removing 'const' did not work and something more is needed.
> 
> your first fix works perfect for me. Could please describe what the error
> is ?

With fresh pair of eyes I must agree and it really does work. The freeze during boot must
have been related to something else and the v2 can be forgotten.

-- Mauri

[PATCH v3 0/1] MIPS: fix compilation error

[Mauri Sandberg]

Hello,

Cleaned up the commit message and added reviewed-by, tested-by and Cc: tags.

Cheers,
Mauri

--

Notes
 v2:
  - errorneous proposal to revert whole commit. withdrawn.
 v3:
  - as v1.
  - Added Reviewed-by: and Tested-By for Thomas Bogendoerfer
  - reworded commit message
  - added Cc: trivial@kernel.org

rangediff v1...v3
1:  cff3565c8f48 ! 1:  e4e83543be07 MIPS: kernel: setup.c: fix compilation error
    @@ Metadata
      ## Commit message ##
         MIPS: kernel: setup.c: fix compilation error
     
    -    Developing against mips/mips-next I get a compilation error.
    -    With the attached patch compilation succeeds.
    +    With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
    +    compilation error. This patch fixes it.
     
         Build log:
         ...
    @@ Commit message
           CC      fs/attr.o
         make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
          Error 1
    -    make[3]: *** [../scripts/Makefile.build:514: arch/mips/kernel] Error 2
    -    make[2]: *** [/home/ubuntu/git/linux/Makefile:1849: arch/mips] Error 2
    -    make[2]: *** Waiting for unfinished jobs....
         ...
     
         Root cause seems to be:
    -    commit b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
    +    Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
     
         Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
    +    Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    +    Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
    +    Cc: trivial@kernel.org
     
      ## arch/mips/kernel/setup.c ##
     @@

Mauri Sandberg (1):
  MIPS: kernel: setup.c: fix compilation error

 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


base-commit: 19f0e8cddf0f136112acaaf02dab2cee35b56439
-- 
2.25.1

[PATCH v3 1/1] MIPS: kernel: setup.c: fix compilation error

[Mauri Sandberg]

With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
compilation error. This patch fixes it.

Build log:
...
  CC      kernel/locking/percpu-rwsem.o
../arch/mips/kernel/setup.c:46:39: error: conflicting types for
'__appended_dtb'
 const char __section(".appended_dtb") __appended_dtb[0x100000];
                                       ^~~~~~~~~~~~~~
In file included from ../arch/mips/kernel/setup.c:34:
../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
of '__appended_dtb' was here
 extern char __appended_dtb[];
             ^~~~~~~~~~~~~~
  CC      fs/attr.o
make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
 Error 1
...

Root cause seems to be:
Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")

Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: trivial@kernel.org
---
 arch/mips/kernel/setup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 279be0153f8b..23a140327a0b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -43,7 +43,7 @@
 #include <asm/prom.h>
 
 #ifdef CONFIG_MIPS_ELF_APPENDED_DTB
-const char __section(".appended_dtb") __appended_dtb[0x100000];
+char __section(".appended_dtb") __appended_dtb[0x100000];
 #endif /* CONFIG_MIPS_ELF_APPENDED_DTB */
 
 struct cpuinfo_mips cpu_data[NR_CPUS] __read_mostly;
-- 
2.25.1

Re: [PATCH v3 1/1] MIPS: kernel: setup.c: fix compilation error

[Thomas Bogendoerfer]

On Mon, Mar 29, 2021 at 03:31:36PM +0300, Mauri Sandberg wrote:
> With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
> compilation error. This patch fixes it.
> 
> Build log:
> ...
>   CC      kernel/locking/percpu-rwsem.o
> ../arch/mips/kernel/setup.c:46:39: error: conflicting types for
> '__appended_dtb'
>  const char __section(".appended_dtb") __appended_dtb[0x100000];
>                                        ^~~~~~~~~~~~~~
> In file included from ../arch/mips/kernel/setup.c:34:
> ../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
> of '__appended_dtb' was here
>  extern char __appended_dtb[];
>              ^~~~~~~~~~~~~~
>   CC      fs/attr.o
> make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
>  Error 1
> ...
> 
> Root cause seems to be:
> Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
> 
> Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
> Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> Cc: trivial@kernel.org
> ---
>  arch/mips/kernel/setup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

applied to mips-fixes. I dropped the Tested-by as this would imply
for me booting that kernel, which I didn't.

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH v3 1/1] MIPS: kernel: setup.c: fix compilation error

[Maciej W. Rozycki]

On Tue, 30 Mar 2021, Thomas Bogendoerfer wrote:

> > With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
> > compilation error. This patch fixes it.
> > 
> > Build log:
> > ...
> >   CC      kernel/locking/percpu-rwsem.o
> > ../arch/mips/kernel/setup.c:46:39: error: conflicting types for
> > '__appended_dtb'
> >  const char __section(".appended_dtb") __appended_dtb[0x100000];
> >                                        ^~~~~~~~~~~~~~
> > In file included from ../arch/mips/kernel/setup.c:34:
> > ../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
> > of '__appended_dtb' was here
> >  extern char __appended_dtb[];
> >              ^~~~~~~~~~~~~~
> >   CC      fs/attr.o
> > make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
> >  Error 1
> > ...
> > 
> > Root cause seems to be:
> > Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
> > 
> > Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
> > Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > Cc: trivial@kernel.org
> > ---
> >  arch/mips/kernel/setup.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> applied to mips-fixes. I dropped the Tested-by as this would imply
> for me booting that kernel, which I didn't.

 Why removing the `const' qualifier rather than adding it to the 
declaration?  Is the DTB supposed to be r/w for the kernel?

  Maciej

Re: [PATCH v3 1/1] MIPS: kernel: setup.c: fix compilation error

[Florian Fainelli]

On 3/31/2021 3:55 PM, Maciej W. Rozycki wrote:
> On Tue, 30 Mar 2021, Thomas Bogendoerfer wrote:
> 
>>> With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
>>> compilation error. This patch fixes it.
>>>
>>> Build log:
>>> ...
>>>   CC      kernel/locking/percpu-rwsem.o
>>> ../arch/mips/kernel/setup.c:46:39: error: conflicting types for
>>> '__appended_dtb'
>>>  const char __section(".appended_dtb") __appended_dtb[0x100000];
>>>                                        ^~~~~~~~~~~~~~
>>> In file included from ../arch/mips/kernel/setup.c:34:
>>> ../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
>>> of '__appended_dtb' was here
>>>  extern char __appended_dtb[];
>>>              ^~~~~~~~~~~~~~
>>>   CC      fs/attr.o
>>> make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
>>>  Error 1
>>> ...
>>>
>>> Root cause seems to be:
>>> Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
>>>
>>> Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
>>> Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
>>> Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
>>> Cc: trivial@kernel.org
>>> ---
>>>  arch/mips/kernel/setup.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> applied to mips-fixes. I dropped the Tested-by as this would imply
>> for me booting that kernel, which I didn't.
> 
>  Why removing the `const' qualifier rather than adding it to the 
> declaration?  Is the DTB supposed to be r/w for the kernel?

In premise the appended dtb could be modified by the kernel early on if
needed even before being handed over to __dt_setup_arch(), so keeping it
read/write for the kernel sort of makes sense. No upstream platform
seems to do that though. If we were to re-instate the const qualifier
(only build tested) the path of least resistance appears to be this:

diff --git a/arch/mips/include/asm/bootinfo.h
b/arch/mips/include/asm/bootinfo.h
index 5be10ece3ef0..31919e1e2dc7 100644
--- a/arch/mips/include/asm/bootinfo.h
+++ b/arch/mips/include/asm/bootinfo.h
@@ -115,14 +115,14 @@ extern unsigned long fw_arg0, fw_arg1, fw_arg2,
fw_arg3;
 #include <linux/libfdt.h>
 #include <linux/of_fdt.h>

-extern char __appended_dtb[];
+extern const char __appended_dtb[];

 static inline void *get_fdt(void)
 {
        if (IS_ENABLED(CONFIG_MIPS_RAW_APPENDED_DTB) ||
            IS_ENABLED(CONFIG_MIPS_ELF_APPENDED_DTB))
                if (fdt_magic(&__appended_dtb) == FDT_MAGIC)
-                       return &__appended_dtb;
+                       return (void *)&__appended_dtb;

        if (fw_arg0 == -2) /* UHI interface */
                return (void *)fw_arg1;
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 23a140327a0b..279be0153f8b 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -43,7 +43,7 @@
 #include <asm/prom.h>

 #ifdef CONFIG_MIPS_ELF_APPENDED_DTB
-char __section(".appended_dtb") __appended_dtb[0x100000];
+const char __section(".appended_dtb") __appended_dtb[0x100000];
 #endif /* CONFIG_MIPS_ELF_APPENDED_DTB */

 struct cpuinfo_mips cpu_data[NR_CPUS] __read_mostly;


-- 
Florian

Re: [PATCH v3 1/1] MIPS: kernel: setup.c: fix compilation error

[Mauri Sandberg]

> ----------------------------------------
> From: Maciej W. Rozycki <macro@orcam.me.uk>
> On Tue, 30 Mar 2021, Thomas Bogendoerfer wrote:
> > > With ath79_defconfig enabling CONFIG_MIPS_ELF_APPENDED_DTB gives a
> > > compilation error. This patch fixes it.
> > > 
> > > Build log:
> > > ...
> > >   CC      kernel/locking/percpu-rwsem.o
> > > ../arch/mips/kernel/setup.c:46:39: error: conflicting types for
> > > '__appended_dtb'
> > >  const char __section(".appended_dtb") __appended_dtb[0x100000];
> > >                                        ^~~~~~~~~~~~~~
> > > In file included from ../arch/mips/kernel/setup.c:34:
> > > ../arch/mips/include/asm/bootinfo.h:118:13: note: previous declaration
> > > of '__appended_dtb' was here
> > >  extern char __appended_dtb[];
> > >              ^~~~~~~~~~~~~~
> > >   CC      fs/attr.o
> > > make[4]: *** [../scripts/Makefile.build:271: arch/mips/kernel/setup.o]
> > >  Error 1
> > > ...
> > > 
> > > Root cause seems to be:
> > > Fixes: b83ba0b9df56 ("MIPS: of: Introduce helper function to get DTB")
> > > 
> > > Signed-off-by: Mauri Sandberg <sandberg@mailfence.com>
> > > Reviewed-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > > Tested-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
> > > Cc: trivial@kernel.org
> > > ---
> > >  arch/mips/kernel/setup.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > applied to mips-fixes. I dropped the Tested-by as this would imply
> > for me booting that kernel, which I didn't.
> 
>  Why removing the `const' qualifier rather than adding it to the 
> declaration?  Is the DTB supposed to be r/w for the kernel?

That is a good point. I tried it too but to my untrained eye it seemed to break up things
more and I didn't have enough in-depth knowledge to touch things elsewhere.

-- Mauri